Injection molding footwear

Abstract

Method of making casual footwear including a knitted fabric upper, a woven insole portion, and an injection-molded sole is produced in a mold cycle of 45-second duration, as opposed to five or six minutes heretofore generally required, or the +2 minutes with the latest known materials. Molding conditions and materials are carefully controlled, and substantial penetration of the woven and knitted fabrics by the injected material is achieved. The woven insole portion prevents the flowing plastic from pushing the upper over the last. Ethylene/ethyl acrylate copolymer, polyvinyl chloride and styrene butadiene are preferred sole thermoplastics.

What is claimed is: 
     
       1. In a process for producing footwear having a molded sole portion attached to a knitted fabric upper, wherein said upper is fitted over a last, the last and upper are clamped over the top of an open mold cavity, and a liquid thermoplastic material is injected into said cavity to form, upon cooling, said molded sole, the improvements comprising providing said upper with an attached, tightly woven insole portion smaller than said molded sole, said upper and last being dimensioned so as to require stretching of said upper over said last thereby creating openings between the stitches of said knitted upper, said insole portion preventing said thermoplastic from pushing said upper on said last. 
     
     
       2. The process as claimed in claim 1, wherein said knitted fabric is elasticized. 
     
     
       3. The process as claimed in claim 1, wherein said thermoplastic material is selected from the group consisting of ethylene/ethyl acrylate, styrene butadiene and polyvinyl chloride. 
     
     
       4. A process for producing footwear having a fabric upper and an integral injection-molded sole portion comprising: preforming a knitted fabric upper with a woven insole portion smaller than said molded sole;   fitting said upper over a last, said upper being dimensioned so as to require stretching thereover, thereby creating openings between the stitches of said upper around the peripheral surface of said last;   clamping said last and upper over an open mold cavity;   injecting a liquid thermoplastic material into said cavity, said material penetrating through said openings around the periphery of said insole portion while chilling said mold; and   removing said last from said mold and said footwear from said last.   
     
     
       5. The process as claimed in claim 4, wherein said knitted fabric is elasticized. 
     
     
       6. The process as claimed in claim 4, wherein said thermoplastic material is selected from the group consisting of ethylene/ethyl acrylate, styrene butadiene and polyvinyl chloride.